Radio variability in radio-quiet quasars and low-luminosity AGN

We report on two surveys of radio-weak AGN to look for radio variability. We find significant variability with an RMS of 10-20% on a time scale of months in radio-quiet and radio-intermediate quasars. This exceeds the variability of radio cores in radio-loud quasars (excluding blazars), which vary only on a few percent level. The variability in radio-quiet quasars confirms that the radio emission in these sources is indeed related to the AGN. The most extremely variable source is the radio-intermediate quasar III Zw 2, which was recently found to contain a relativistic jet. In addition, we find large-amplitude variability (up to 300% peak-to-peak) in a sample of nearby low-luminosity AGN, LINERs and dwarf Seyferts, on a time scale of 1.5 years. The variability could be related to the activity of nuclear jets responding to changing accretion rates. Simultaneous radio/optical/X-ray monitoring also of radio-weak AGN, and not just of blazars, is therefore a potentially powerful tool to study the link between jets and accretion flows.